1. The flip image Block

The flip image block, available in the Image menu, will take the image that is stored in an image object and flip it across a specified line, such as the y-axis:

2. Flipping Works Like a Mirror

The specified flipping line acts like a mirror. The result is easiest to see when the line is the y-axis (like a vertical mirror). If the initial image is centered at the point x = 6, y = 6, the flip image (y-axis) block will change the image to its mirror image at the point x = -6, y = 6. Here's the code and result (with the labels drawn separately):

If we instead flip it across the x-axis, it looks like this (the y values of the image are changed from positive to negative):

Example 1 shows how it works using a dolphin image. It's recommended to use the  Step  button to step through the code one block at a time to see how the flipping works.

 IMPORTANT: When we use the flip image block to flip an image stored in an image object, the stored image is actually changed. That is, it remains in the new flipped orientation and location. So if we do a second flip with the image object, the flip will affect the image at its current flipped orientation and location, not the original image. 

Example 1 demonstrates this by creating and displaying an initial image of a dolphin, and then flipping it three times, displaying it after each flip.

3. Flipping Across the y = x and y = -x Lines

The y = x line is a diagonal line at an angle of 45 degrees. When we flip an image across that line it looks like this:

And flipping across the y = -x line looks like this:

Examples 2 and 3 show how it works. Example 3 also places three colored dots on the image to help see how the flips work.

4. Flipping Across Any Vertical or Horizontal Line

We can use any vertical or horizontal line for the flipping line, not just the x-axis or y-axis. This code specifies the vertical line x = 2 as the flipping line, with the result shown below (with the blue dotted line and labels drawn separately):

Here are two more examples using the horizontal line y = 4:

Example 4 shows how it works.